Embodiments of the present invention relate to systems, methods, and devices for imaging and, more particularly, to optical coherence tomography (OCT) imaging techniques.
Optical coherence tomography (OCT) is a non-invasive imaging technique that is often used in clinical applications to obtain high-resolution cross-sectional images of subsurface in vivo (living) biological tissue and other materials. For example, OCT imaging techniques are used in a variety of medical fields, including ophthalmology, cardiology, and dermatology, to name just a few. In particular, OCT imaging is popular in ophthalmology for ocular diagnostic purposes, where it may be used to obtain detailed images of a retina or other structures within a human eye. For instance, OCT imaging has been known to be capable of delineating layers of the retina with a very high degree of clarity. Currently, some OCT imaging techniques are capable of producing images at micrometer, or even sub-micrometer, scale resolutions.
OCT imaging systems operate on the principle of interferometry, in which subsurface light reflections are resolved to provide a tomographic visualization of a sample (e.g., the tissue or object being imaged). Generally, OCT imaging systems split light provided by a light source along a first optical path containing the sample, usually referred to as a “sample arm,” and a second optical path containing a reference mirror, usually referred to as a “reference arm.” The combination of reflected light from the sample arm and reflected reference light from the reference arm gives rise to an interference pattern, but generally only if light from both arms have traveled the “same” optical distance, wherein “same” means a difference of less than a coherence length. Thus, when acquiring images using an OCT imaging system, an operator may be tasked with ensuring that the reference and sample arms have the same path length, which may involve adjusting the length of the reference arm manually, so that an interference pattern is properly generated. As can be appreciated, due to variations in the size or dimensions of a particular sample type, such as human eyes, the path length of the sample arm may vary, thus requiring the path length of the reference arm to vary to match the sample arm. Moreover, because the path lengths are to be adjusted until they match (e.g., typically with a tolerance of a few millimeters, or even micrometers), this task may not only be difficult to perform accurately, but may also be subject to human error.
Further, once the reference and sample arms are matched, the operator may also be tasked with manually adjusting the focal position of one or more focusing lenses of the OCT system to ensure that the acquired image is in focus. As can be appreciated, manually determining an optimal focusing position may be difficult, particularly when such adjustments are sometimes on the order of micrometers (μm). Moreover, since the focus quality of such adjustments may be subjectively determined based on an operator's vision, what is perceived to be an optimal focus position for the lens may not always correspond to what is actually the optimal focus position. Accordingly, there exists a need for an OCT imaging system that is capable of automating the manual tasks discussed above, thus removing the labor-intensive aspects of OCT imaging while improving the performance and accuracy of OCT imaging systems.